In order to exploit this vulnerability the MySQL server must be accessible to the attacker. (i.e. if the attacker doesn't have local access and the MySQL server is running in a Unix socket, no worries then. But if the service is available over the Internet, anyone can potentially access it with root privileges potentially compromising the entire server depending on the configuration.)

Reports has begun to come in on e.g. Twitter stating that RHEL (Red Hat Enterprise Linux) doesn't seem to be affected, but that Ubuntu (and most likely Debian) are affected among other distributions.